1. Technical Field
Example embodiments relate generally to semiconductor integrated circuits, and more particularly to a lock-in amplifier, an integrated circuit and a portable measurement device including the lock-in amplifier.
2. Discussion of the Related Art
In case of an AC signal having a very small amplitude, an amplification of the AC signal is required for measurement of the signal. The noise is amplified together with the AC small signal and thus noise filtering is typically accompanied with the signal amplification. A band-pass filter (BPF) may be used for detection of a particular frequency component. In this case, the noise remains in the pass band of the BPF and the small signal is buried in the noise. In addition, it is difficult to design a BPF having a sufficiently-narrow pass band.